The present invention relates to an improved wellhead structure and to the method of assembling such structure. Compact wellheads have been used to provide a suspension and sealing system for casing and tubing strings from a single head which reduces the stack-up height and reduces the number of connections required. Also, with such compact wellhead the blowout preventer stack is not removed during installation of the casing and tubing. Normally, with the use of such compact heads, the last string of pipe with the casing hangers attached is run into the well and the casing hangers are landed rather than using slips to support a casing string and cutting the string for the installation of a hanger thereon. This system would utilize the slips for support and the elastomeric seals to provide the annulus seal.
Some hangers have utilized slips to engage and support the well string. U.S. Pat. Nos. 2,920,909 and 3,311,168 disclose such structure. Other hangers have had an external shoulder which is adapted to seat on an internal housing seat, such as is shown in U.S. Pat. Nos. 3,561,527 and 3,797,864. Such hangers are provided normally with external threads on their lower ends and have their well strings threaded thereon.
In the past it has been known that a portion of a remote connector could be remotely cold formed onto the end of a subsea pipeline so that a repair section would be connected to the existing pipeline. Examples of cold forming are shown in U.S. Pat. Nos. 3,432,916, 4,330,144; and 4,388,752. 4,662,663 suggests the use of a material within the grooves to compensate for any build-up of pressure therein during forming. U.S. Pat. No. 2,134,311 discloses the roll forging of the upper end of a string into grooves within the interior of casing head to support and seal the upper end of the string therein.
Reference is also made to copending application Serial No. 07/044,409, filed Apr. 30, 1987, now continuation application Ser. No. 07/217,376, filed July 11, 1988, which discloses the securing of a tubular member within an annular well member in a cold forging operation.